Add a couple of Kubernetes questions and exercises

In addition, changed the order of some Linux questions.

exercises/kubernetes/replicaset_01.md

@@ -8,4 +8,7 @@ Learn how to create and view ReplicaSets
 
 1. Create a ReplicaSet with 2 replicas. The app can be anything.
 2. Verify a ReplicaSet was created and there are 2 replicas
-3. Remove the ReplicaSet you've created
+3. Delete one of the Pods the ReplicaSet has created
+4. If you'll list all the Pods now, what will you see?
+5. Remove the ReplicaSet you've created
+6. Verify you've deleted the ReplicaSet

exercises/kubernetes/replicaset_02.md

@@ -0,0 +1,12 @@
+## ReplicaSet 102
+
+#### Objective
+
+Learn how to operate ReplicaSets
+
+#### Instructions
+
+1. Create a ReplicaSet with 2 replicas. The app can be anything.
+2. Verify a ReplicaSet was created and there are 2 replicas
+3. Remove the ReplicaSet but NOT the pods it created
+4. Verify you've deleted the ReplicaSet but the Pods are still running

exercises/kubernetes/replicaset_03.md

@@ -0,0 +1,14 @@
+## ReplicaSet 103
+
+#### Objective
+
+Learn how labels used by ReplicaSets
+
+#### Instructions
+
+1. Create a ReplicaSet with 2 replicas. Make sure the label used for the selector and in the Pods is "type=web"
+2. Verify a ReplicaSet was created and there are 2 replicas
+3. List the Pods running
+4. Remove the label (type=web) from one of the Pods created by the ReplicaSet
+5. List the Pods running. Are there more Pods running after removing the label? Why?
+6. Verify the ReplicaSet indeed created a new Pod

exercises/kubernetes/solutions/replicaset_01_solution.md

@@ -0,0 +1,62 @@
+## ReplicaSet 01 - Solution
+
+1. Create a ReplicaSet with 2 replicas. The app can be anything.
+
+```
+cat >> rs.yaml <<EOL
+apiVersion: apps/v1
+kind: ReplicaSet
+metadata:
+  name: web
+  labels:
+    app: somewebapp
+    type: web
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      type: web
+  template:
+    metadata:
+      labels:
+        type: web
+    spec:
+      containers:
+      - name: httpd
+        image: registry.redhat.io/rhscl/httpd-24-rhel7
+EOL
+
+kubectl apply -f rs.yaml
+```
+
+2. Verify a ReplicaSet was created and there are 2 replicas
+
+```
+kubectl get rs
+# OR a more specific way: kubectl get -f rs.yaml
+```
+
+3. Delete one of the Pods the ReplicaSet has created
+
+```
+kubectl delete po <POD_NAME>
+```
+
+4. If you'll list all the Pods now, what will you see?
+
+```
+The same number of Pods. Since we defined 2 replicas, the ReplicaSet will make sure to create another Pod that will replace the one you've deleted.
+```
+
+5. Remove the ReplicaSet you've created
+
+```
+kubectl delete -f rs.yaml
+```
+
+6. Verify you've deleted the ReplicaSet
+
+```
+kubectl get rs
+# OR a more specific way: kubectl get -f rs.yaml
+```

exercises/kubernetes/solutions/replicaset_02_solution.md

@@ -0,0 +1,62 @@
+## ReplicaSet 02 - Solution
+
+1. Create a ReplicaSet with 2 replicas. The app can be anything.
+
+```
+cat >> rs.yaml <<EOL
+apiVersion: apps/v1
+kind: ReplicaSet
+metadata:
+  name: web
+  labels:
+    app: somewebapp
+    type: web
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      type: web
+  template:
+    metadata:
+      labels:
+        type: web
+    spec:
+      containers:
+      - name: httpd
+        image: registry.redhat.io/rhscl/httpd-24-rhel7
+EOL
+
+kubectl apply -f rs.yaml
+```
+
+2. Verify a ReplicaSet was created and there are 2 replicas
+
+```
+kubectl get rs
+# OR a more specific way: kubectl get -f rs.yaml
+```
+
+3. Remove the ReplicaSet but NOT the pods it created
+
+```
+kubectl delete -f rs.yaml --cascade=false
+```
+
+4. Verify you've deleted the ReplicaSet but the Pods are still running
+
+```
+kubectl get rs # no replicas
+kubectl get po # Pods still running
+```
+
+5. Create again the same ReplicaSet, without changing anything
+
+```
+kubectl apply -f rs.yaml
+```
+
+6. Verify that the ReplicaSet used the existing Pods and didn't create new Pods
+
+```
+kubectl describe rs web  # You should see there are no new events and if you list the pods with 'kubectl get po -f rs.yaml` you'll see they have the same names
+```

exercises/kubernetes/solutions/replicaset_03_solution.md

@@ -0,0 +1,61 @@
+## ReplicaSet 03 - Solution
+
+1. Create a ReplicaSet with 2 replicas. Make sure the label used for the selector and in the Pods is "type=web"
+
+```
+cat >> rs.yaml <<EOL
+apiVersion: apps/v1
+kind: ReplicaSet
+metadata:
+  name: web
+  labels:
+    app: somewebapp
+    type: web
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      type: web
+  template:
+    metadata:
+      labels:
+        type: web
+    spec:
+      containers:
+      - name: httpd
+        image: registry.redhat.io/rhscl/httpd-24-rhel7
+EOL
+
+kubectl apply -f rs.yaml
+```
+
+2. Verify a ReplicaSet was created and there are 2 replicas
+
+```
+kubectl get rs
+# OR a more specific way: kubectl get -f rs.yaml
+```
+
+3. List the Pods running and save the output somewhere
+
+```
+kubectl get po > running_pods.txt
+```
+
+4. Remove the label (type=web) from one of the Pods created by the ReplicaSet
+
+```
+kubectl label pod <POD_NAME> type-
+```
+
+5. List the Pods running. Are there more Pods running after removing the label? Why?
+
+```
+Yes, there is an additional Pod running because once the label, used as a matching selector, was removed, the Pod became independant meaning, it's not controlled by the ReplicaSet anymore and the ReplicaSet was missing replicas based on its definition so, it created a new Pod.
+```
+
+6. Verify the ReplicaSet indeed created a new Pod
+
+```
+kubectl describe rs web
+```